Amorphous aluminosilicates are generally produced by a process in which an aqueous solution of either sodium aluminate or aluminum sulfate is mixed in an appropriate proportion with an aqueous solution of sodium silicate at an appropriate temperature and concentration, if desired further with an aqueous solution of sodium hydroxide, and the amorphous aluminosilicate thus synthesized is separated from the mother liquor by filtration or another means and then cleaned to remove the residual mother-liquor components including the excess alkali. In most cases, the amorphous aluminosilicate obtained is finally dried in some way.
Since the aluminosilicate thus produced actually has some degree of oily substance-absorbing and ion-exchanging properties and other properties, it has been thought to be useful for use as various industrial materials including a catalyst, a catalyst base, an additive for resins, and an ion exchanger.
An example of the above process is disclosed in JP-B-61-25653. (The term "JP-B" as used herein means an "examined Japanese patent publication.") In this prior art process, an amorphous aluminosilicate having high oily substance absorption ability and excellent ion exchange ability is produced by regulating the concentration of an alkali metal oxide to a value within a given range.
However, the amorphous aluminosilicate produced by conventional processes highly tends to aggregate and hence has the following drawbacks. In the case where the amorphous aluminosilicate is used, e.g., as a carrier, a homogeneous product is difficult to obtain even after sufficient mixing. In use in water, aggregates of the amorphous aluminosilicate sediment, making rapid ion capture impossible. When used as a detergent builder, the amorphous aluminosilicate causes troubles such as adhesion of aluminosilicate aggregates to clothes. Moreover, in the case of addition to a resin, etc., it is exceedingly difficult to homogeneously disperse the amorphous aluminosilicate because it shows poor dispersibility due to its strong tendency to aggregate.
With respect to oil absorption ability, the amorphous aluminosilicate produced by conventional processes has the following drawbacks. Since the conventional amorphous aluminosilicate has a large amount of large pores of, e.g., 10.sup.5 angstroms or larger, these pores are readily destroyed physically, e.g., by pulverization, resulting in a considerable decrease in oil absorption ability. The amorphous aluminosilicate also shows low holding power due to the small contact area where the supported substance is in contact with the aluminosilicate, so that the supported ingredient oozes out with the lapse of time. In contrast, if an amorphous aluminosilicate has a large amount of too small pores, it not only shows strong tendency to aggregate, but also has a drawback that most ingredients once supported thereon cannot diffuse because the ingredients are too tenaciously supported due to large contact area where the ingredients are in contact with the aluminosilicate or because the pore size is too small for the size of the supported molecules. Thus, the amorphous aluminosilicate having a large amount of too small pores also cannot always produce the desired effect (JP-A-6-227811). (The term "JP-A" as used herein means an "unexamined published Japanese patent application".)
There has hence been a desire for an amorphous aluminosilicate which is unaffected by pulverization and has a regulated pore structure which enables an ingredient supported thereon to fully perform its function.
With respect to ion exchange ability, the amorphous aluminosilicate produced by conventional processes has the following drawbacks. It is difficult to make the amorphous aluminosilicate stably exhibit high ion exchange ability because the ion exchange capacity thereof decreases even during the production thereof due to, for example, the heat treatment for drying, and because the amorphous aluminosilicate suffers a considerable decrease in ion exchange ability during only several-month storage even at room temperature. Hence, when the conventional amorphous aluminosilicate is used as an ion exchanger for, e.g., the removal of free metal ions, the ion exchange ability of the aluminosilicate is insufficient because of the insufficient exchange capacity thereof.
Consequently, the actually utilizable ion exchange capacities of conventional amorphous aluminosilicates have been up to about 50% of their theoretical exchange capacities calculated from the chemical compositions. Although the cause of such low actual exchange capacities has not been elucidated, it is thought that the sites which take part in ion exchange are severely affected, e.g., by the state of the Al atoms, Na atoms, and water molecules contained in the aluminosilicate framework or by the generation of a surface state which inhibits ion diffusion.
Consequently, there has been a strong desire for an amorphous aluminosilicate which is free from these problems.